Umm, wouldn't move them now, and having seen how they've developed over time I think they are at the right school for them (superselective grammar).
BUT that is because of the way the local system influences the local schools- the top academically able cohort are at the grammars (why pay if you get a state place, even if you can do so) then the slightly less able are at the indies (only know 1 person who turned down a grammar place for her son in favour of an indie place).. THe comps are very vocational and are good at that for the kids who suit that way of learning- they aren't so good for the able but not high flighig kids though.
At 11 I'd have said indie if we could have done, simply because I'd hate them to be "struggling" at grammar school and I really , honestly had no idea at that point if they were academically good or very able.
As it's turned out , luckily I guess , they are/have (DD1 has left school now) taking it all in their stride.
Naiively, 8yrs into having kids at superselective schools it's only just dawned on my that lots of them aren't only tutored hard for the exams, but are then tutored to keep up at school- that would be a horrid situation to be in I think.
We had a horrible choice to make with and on behalf of DD2- she got a good academic scholarship to a local independent- but they wanted us to sign up to keep her there till 18, and we (fortunately correctly I think) rather thought she'd be better at grammar. But that was really difficult. I think if it'd been the eldest and we had no experience of the girl's grammar i wouldhave been near impossible.
I am very aware that DH was privately educated and is clearly a lovely chap and very able, but felt he was always a lesser person academically than a lot of his friends, whereas I went to a very ordinary comp in the early 1980's and achieved academically only by the sweat of my brow and the fortune to have a best mate who was even brighter than me. We both sat 4 A levels (against the schools wishes).... she went to Cambridge and I studied my course at uni- both "great successes for the school " (boo hiss!) as we were the first to do either in the history of the school!